The winding overhangs of power plant generators are excited to vibrate during operation and during electrical faults. Excessively high vibrations can lead to damage to the winding overhangs, and may destroy the generator.
Hitherto, the state of a winding overhang in the generator has been determined by bump tests, which are complicated to perform. To this end, the generator to be examined has to be stopped, the cooling gas evacuated and the generator opened. With this method, the eigenfrequencies and eigenmodes of the winding overhang can be determined well. However, these frequencies shift during operation because of the operating temperatures, which is disadvantageous. Thus, an assessment of the condition of the winding overhang can be carried out economically only at relatively large time intervals. Continuous recording of the winding overhang vibrations at discrete positions is already carried out on individual winding overhangs, however suitable methods for evaluation are lacking.